Layer Separation

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Layer Separation

Postby james_coleman » 2013-Mar-Fri-13-Mar

All,

I'm getting up and going with my PB+ and overall, I'm pleased with the results. I'm seeing some layer separation at the beginning of nearly all my prints (see picture). I've been using the 3mm natural ABS supplied by printrbot. I print on glass with kapton tape. My sli3er settings are below. I can't post my full sli3er settings because it looks too spammy, but my bed is at 85 degrees, and my extruder is at 230 degrees. Any suggestions for improving my results?

Thanks!
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Layer Separation

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Re: Layer Separation

Postby halley » 2013-Mar-Fri-14-Mar

Nice print.

Slic3r has a setting for the height of the first layer. It's a challenge to find the right height that sticks properly, and also minimizes that layer-one-to-layer-two spacing effect. I'm all ears on whether there's a good workaround that works in all cases. I expect the next version of Slic3r will have a LOT of tweaks and maybe this is one.
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Re: Layer Separation

Postby plexus » 2013-Mar-Fri-15-Mar

Give KISSlicer a try also. there is a KISSlicer thread somewhere on the forum. ensure your Z is calibrated accruately. also ensure you are getting the material to the right temp - my PB is 10-20C cooler than what it reports. to get 230C i need to set it at 248C (so i use 250C) [i had to update the firmware to allow higher temps than 250C]. and print somewhat slowly around the 15-25mm/s mark for the first few layers until you get things dialed in.
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Re: Layer Separation

Postby james_coleman » 2013-Mar-Fri-23-Mar

Thanks for the advice! I'll give KISS slicer a try and make sure my temps are accurate!
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Re: Layer Separation

Postby eckerput » 2013-Mar-Mon-09-Mar

Higher extruder temps will help with layer to layer bonding at the expense of more oozing and melting on smaller parts. One other thing to watch out for is when you're layer heights get too close to your nozzle diameter the nozzle won't flatten out the bead of plastic when passes. I wouldn't use a layer height more than 75% of the nozzle diameter if I needed good bonding.
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Re: Layer Separation

Postby ivymike1031 » 2013-Jun-Wed-10-Jun

There are some things you can do to help design out warping and layer separation as well, depending on the part.

When a part is being printed, each layer is put down hot and then contracts as it cools. There is some time between deposition of each layer in a particular location, because the print head must move all around to get every position in the layer. This means that each layer ends up tugging "inward" on the layer below it. With enough layers pulling each other, it's not surprising that the bonds between lower layers get overloaded and the layers start to peel apart. While making stronger bonds (via higher temp) and reducing the thermal differences between layers (via heated print bed / environment) can help, there are design characteristics which can also help.

Based on my comments above, one can deduce that longer layers would be more subject to peeling apart than shorter layers, as there is more distance over which cooling-related shrinking can occur. Also, the amount of time between the deposition of subsequent layers can influence the degree to which each layer tugs on the one below it - if they all came out at the same temperature at one time, then while cooling they would all stay at about the same length as each other and there would be very little "peeling force" to help separate the layers. It may be possible to print your part in another orientation, such that each layer takes less time to print before the next is started - a "tall and narrow" setup instead of "short and fat".

Alternatively, one can incorporate "break points" within layers to help keep the peeling force to a minimum. The picture below shows a basket/box that I printed to hold trash bags behind my trash can. At the outset I was printing the part with solid walls...and I ran into significant layer separation problems. I terminated the print early and used a knife to give myself a flat-ish top surface ... but I found that the box was not deep enough to accomplish the intended purpose. I revised the part to include breaks in the walls, and then printed just an upper section which I attached to the lower section with superglue. As you can see in the pic, there is essentially no layer separation in the upper part vs. very significant separation in the lower part, despite the remainder of the printer settings remaining fixed (same extrude temp, same bed temp, same room, same bed prep, etc).

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Re: Layer Separation

Postby Tdeagan » 2013-Jun-Sat-00-Jun

That's a great insight! It makes me wonder how small the breaks can be. I'm starting to fantasize about a setting in Slic3r that adds single step (or double or whatever,) breaks in some useful pattern. We could have choices for wall patterns like we do for infill. (Wow. I really need to get out of my shop more. My fantasies have really lost a lot of their pizzaz.)
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Re: Layer Separation

Postby ivymike1031 » 2013-Jun-Sat-05-Jun

I've made a fan shroud with barely-visible breaks, and they were adequate to stop the separation I'd had without them. There are limits to what the stl files can represent, I think.
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